Immunoassays have been used in recent years to detect the presence of infectious diseases. In order for the assay to be useful, it must detect a particular organism with a high degree of reliability. In most cases, this requires the isolation and reaction of antigens peculiar to the organism with corresponding antibodies. For the test to be commercially successful, it also needs to be relatively inexpensive, simple to use and rapid.
One such organism which can be detected by immunoassay is herpes simplex virus. Despite the increasing control of various viruses by vaccination or treatment with various anti-viral agents, infection by herpes simplex virus (identified herein as HSV) remains a serious problem. There are two types of HSV: type 1 which occurs mainly around the mouth, and type 2 which occurs primarily around the genital area of the human body. Skin infections and viral encephalitis are but two of the serious results from HSV infection.
Because of the widespread nature of HSV infection, there is considerable interest in having a rapid, simple and reliable test for detection of the causative virus. However, there are several similar viruses which often are indistinguishable from HSV using known diagnostic procedures. Thus, a useful diagnostic test for HSV-1 or HSV-2 must be specific for these viruses only, and not be sensitive to viruses such as Epstein-Barr virus, cytomegalovirus, varicella zoster virus or any other flora.
HSV has been detected using various analytical techniques including electrophoretic, agglutination and enzyme-linked immunoassays (ELISA). In those techniques where an immunological complex is formed between HSV antigen and antibodies thereto, the complex is normally separated from uncomplexed materials in order to improve detection sensitivity. Separation may be accomplished by filtration, centrifugation or affinity chromatography. In most instances, the complex is insolubilized in some manner and washed to remove uncomplexed materials with distilled water, phosphate buffered saline solution or a number of solutions containing nonionic surfactants.
For example, U.S. Pat. No. 4,535,057 (issued Aug. 13, 1985 to Dreesman et al) describes an solid phase assay for viral antigens, such as herpes simplex viral antigen, in which antibody-antigen complex is washed several times with phosphate buffered saline solution containing a nonionic surfactant marketed under the tradename TWEEN 20 (Col. 21, lines 66-67). The pH of such a solution is generally between 7.0 and 7.5.
While such wash solutions are commonly used in immunological methods, there has been continuing need to improve the sensitivity of assays and to reduce unwanted background signal in the detection of HSV.